Supervisory control system



Dec. 27, 1949 Filed Feb. 27, 1946 J. 1'. PURCELL 2,492,766

SUPERVISORY CONTROL SYSTEM 6 She'ets-Sheet l A Fig. I.

- Inventor; James T.Pur-c'el I by His -A'btorney.

Dec. 27, 1949 i J. T. PURCELL 2,492,766

SUPERVISORY CONTROL SYSTEM Filed Feb. 27, 1946 6 Sheets-Sheet 2 Invntor: James T.F ur*ce||, b M

His Attorney.

Dec. 27, 1949 J. T. PURCELL 2,492,766

SUPERVISORY CONTROL SYSTEM Filed Feb. 27, 1946 6 Sheets-Sheet 3 Inventor- James T. Purcell,

by His Attorney.

Dec. 27,1949

Filed Feb. 27, 1946 I Fig.

J. r. PURCELL 6 Shee ts-Sheet 4 Inventor James T.Purcell,

His Attcsr" hey.

Dec. 27, 1949 Filed Feb. 27, 1946 J. T. PURCELL SUPERVI SORY CONTROL SYS TEM 400 L b l l l 5.

T! \i \1 l 6 Sheets-Sheet 5 Inventor- James T.F ur-cell,

His Attorney.

Dec. 27, 1949 J. T. PURCELL SUPERVISORY CQNTROL SYSTEM Filed Feb. 27, 1946 6 Sheets-Sheet 6 Inventor: James T.F urcell,

His Attorney.

Patented Dec. 27, 1949 UNITED STATES PATENT OFFICE 2,492,766 I surrzavisoar coN'raoL sys'rm James T. Purcell, Secanc, Pa'., assignor to General Electric Company, a corporation of New York Application February 27, 1946, Serial No. 650,619

20 Claims.

' operated over a two-wire metallic circuit through insulating transformers or over the simplified type of carrier channel with only very minor changes being required to change from one type of channel to the other.

A still further object of my invention is to provide a new and improved all relay supervisory control system which may be readily changed to take care of additional apparatus units as the system requirements change.

In accordance with a preferred embodiment of my invention, I employ an all relay equipment in which all of the codes contain the same number of current impulses but differ from each other only by the length of the time interval between one or more of the current impulses.

My invention will be better understood from the following description when taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the embodiment of my invention shown in the drawings, which comprise Figs. 1 to 6, inclusive, the supervisory control system is designed to provide control and indication for five remote apparatus units shown in Fig. 6 as circuit breakers AUI to AUB, inclusive. The apparatus and circuits shOWn in Figs. 1 to 3. inclusive, are those located at the control station or dispatcher's oflice while the apparatus and circuit shown in Figs. 4 to 6, inclusive, are those located at the remote station which is connected to the dispatchers office by two line conductors LI and L2.

At the dispatchers ofllce, there is provided a separate group of control keys and indicating lamps for each apparatus unit to be selected and controlled in the remote station. Each group of keys includes a two-position select key, such as SKI for apparatus unit AUI, SK! for apparatus unit AU2, etc., which is operated by the dispatcher when he desires to select a corresponding apparatus unit for operation or indication, and a two-' 2 position disagreement key, such as DKI for apparatus unit AUI, DK2 for apparatus unit AU2, etc., which respectively controls the operation of the corresponding disagreement lamps WI, W2, etc. of the corresponding group of indicating lamps. Each group of indicating lamps includes a red lamp, such as RI for apparatus unit. AUI, R2 for apparatus unit AU2, etc., which when lighted indicates that the corresponding apparatus unit is in its closed position; a green lamp, such as GI for apparatus unit AUI, G2 for apparatus unit AU2, etc., which when lighted indicates that the corresponding apparatus unit is in its open position; a white lamp. such as WI for apparatus unit AUI, W2 for apparatus unit AU2, etc., which when lighted indicates that the position of the corresponding apparatus unit does not correspond with the position" of the associated disagreement key; and an amber lamp, such as AI for apparatus unit AUI, A2 for apparatus unit AU2, etc., which when lighted indicates that the corresponding apparatus unit has been properly selected. Each group of disagreement keys and associated indicating lamps has associated therewith an indi- 5 viduai indicating relay, such as ml for the group individual to apparatus unit AUI, 1R2 for the group individual to apparatus unit AU2, etc., which determines by its position whether the associated red or green lamp is lighted and which cooperates with the associated disagreement key to determine whether the associated white lamp is lighted. The position of each indicating relay in turn is determined by the position of the corresponding apparatus unit in a manner which will be hereinafter described. As shown in Fig. 1, the indicating relays are shown in their deenergized position which is the position they occupy when their associated apparatus units at the remote station are in their open positions. The disagreement keys DKI to DK5, inclusive, are also shown in the positions corresponding to the open positions of their respective apparatus units so that only the green lamps GI to G5, inclusive, are lighted and all of the white and red lamps are not lighted. Each disagreement key is connected in such a manner that if it were in its other posi tion under the conditions assumed, it would connect the associated white lamp and green lamp in series so that both lamps would be simultaneously lighted.

The equipment at the dispatchers ofllce also includes start lamp STL which is lighted when the supervisory equipment at both stations is in its normal-at-rest position and bell ringing relay Q BR which is normally energized and which is when the operation of the supervisory equipment is initiated at the substation in response to one or the apparatus units thereat automatically changing its position.

. When any one oi the select keys is operated while the supervisory equipment is in its normalat-rest position, a selection code impulses corresponding to the operated select key is transmitted over line conductors LI and L2 fromthe dispatchers once to the substation to selectively energize and lock up at the substation the relay in a group of selection relays S'l to 8'5. inclusive. which is individual to the desired apparatus unit. The code which is transmitted to the substation is also registered at the dispatchers oiiice and operates a selection relay Si to 85. Then a selection check code corresponding to the selected selection relay at the substation is transmitted over line conductors Li and L2 from the substation to the dispatchers oflice. If the two codes check properly, the selected apparatus unit may then be operated by the dispatcher operating master close key MCK which causes a closing control code of impulses to be transmitted over line conductors Li and L2 from the dispatchers oiiice to the substation or master trip key MTK which causes a tripping control code of impulses to be transmitted over line conductors Li and L2 from the dispatchers oflice to the substation. If after selecting an apparatus unit for operation the dispatcher desires to check the position of the selected apparatus unit, he may doso by operating master check key CHK which causes an indication check code to be transmitted over line conductors Li and L2 from the dispatcher's oiiice to the. substation. After each operation of the selected apparatus unit and after an indication check code has been transmitted, either a close indication code or a trip indication code, depending upon the position of he selected apparatus unit, is transmitted over line conductors LI and L! from the substation to the dispatchers omce.

In response to any apparatus unit at the sub-' station automatically changing its position, a selection code of impulses corresponding to the changed apparatus unit is transmitted over line conductors LI and L2 from the substation to the dispatchers oflice to selectively energize at the dispatchers ofllce the selection relay individual to the changed apparatus unit and then a selection check code corresponding to the selected selection relay is transmitted over the line conductors from the dispatchers oflice to the substation. If the selection check code checks with the transmitted selection code, an indication code corresponding to the new position of the changed apparatus unit is transmitted to the dispatchers oiiice to selectively operate at the dispatchers oflice the indication relay individual to the changed apparatus unit so that the lamps individual to the operated apparatus unit will indicate the new position thereof.

In the particular embodiment of my invention shown in the drawing, all of the codes consist of four undirectional current impulses of the same length, but the codes diil'er from each other by the time elapsing, i. e., the pause, between the various impulses as will be seen from the following table of the codes:

Apparatus unit AUl-impulse; impulse; impulse;

impulse.

Apparatus unit Alli-impulse; impulse; impulse; pause; impulse. Apparatus unit Alli-impulse; impulse; pause:

impulse; impulse.

Apparatus unit AU4impulse;

impulse: impulse.

Apparatus unit AIR-impulse; pause; impulse;

impulse: pause; impulse.

Closing-impulse; pause; impulse; pause; im-

pulse; impulse.

Tripping-impulse; impulse; pause; impulse;

pau mpuls pause; impulse.

Indication check-impulse; pause; impulse;

pause; impulse; pause; impulse.

Resetting-one impulse normally, but equipment will reset on any number of impulses other thaniour.

The selection and selection check codes arethe same for each apparatus unit and so are the closing and close indication codes and the tripping and trip indication codes.

The pauses which occur between successive impulses and which are not indicated in the above table are materially shorter than the indicated pauses. In a practical embodiment of my invention, the length of pauses which occur between successive impulses and which are not indicated in' the table are about the same length as the impulses, whereas the indicated pauses are about two and one-half times as long as the impulses.

The operation of any select key at the dispatcher's oillce eflects the extinguishment of start lamp STL and the energlzation or start relay ST, which remains energized until the supervisory equipment is released, and the energizetion of sending control relay SC, which when energized eflects the operation 01' a code transmitter comprising line impulse sender relay LS. When energized, relay LS connects the positive terminal of battery BAT to line conductor LI and the negative terminal of battery BAT to line transmission of a series of current impulses over line conductors LI and L2.

At the substation, there is a similar group of relays US, UK and L'R' which is arranged to eifect the transmission of a series of current impulses over line conductors LI and L2, relay L'S' being arranged when energized to connect the positive terminal of battery B'A'T' to conductor LI and the negative terminal of battery B'A'T' to conductor L2.

A group of four counting relays CI to C4, inclusive, is provided at the dispatchers ofllce, and these relays are successively energized and locked up by the four impulses oi the transmitted code. Transfer relay CT is provided for transferring the connections of relays C I to Cl, inclusive, so that they are selectively operated by the proper impulses oi the code. .A similar group of counting relays C'l to 0'4. inclusive, and transfer relay C'T are operated at the substation by the four impulses of each transmitted code.

For producing a relatively long pause between any two of the four impulses of a code transmitted from the dispatchers omce, pause relay PS is provided which when energized interrupts the energizing circuit of impulse sender relay LS. Pause relay BS is arranged to be energized in response to the energization of any one of the counting relays so that a pause may be produced between any two impulses. During the transmission of a selection code from the dispatchers office, the circuit of pause relay P8 is controlled by the particular select key that has been operated; during the transmission of a selection check code from the dispatchers oillce, the circuit is controlled by the particular selection relay that has been energized by the selection code from the substation; and during the transmission of a control code, the circuit is controlled by the particular control key that has been operated. Pause relay PS is not energized during the transmission of a selection code effected by the operation of select key SKI or during the transmission of a selection check code eflected by selection relay SI or S! because there is no pause in that code. Pause relay P8 is energized in response to the energization of counting relay C3 so that a pause is produced between the third and fourth impulses of a selection code effected by the operation of select key 8K2 and of a selection check code effected by selection relay S2 or S2. Pause relay P8 is energized in response to the energization of counting relay C2 so-that a pause is produced between the second and third impulses of a selection code effected by the operation of select key SK3 and of a selection check code effected by selection relay S3 or S3. Pause relay PS is energized in response to the energization of counting relay Cl so that a pause is produced between the first and second impulses of a selection code effected by the operation of select key SK4 and of a selection check code efiected by selection relay S4 or S'4. Pause relay PS is energized in response tothe energization of counting relays Cl and C3 so that a pause is produced between the first and second impulses and between the third and fourth impulses of a selection code effected by the operation of select key SK5 and of a selection check code efiected by selection relay S5 or 8'5. When master control key M'I'K is operated, pause relay PS is energized in response to the energization of counting relays C2 and C3 so that a pause is produced between the second and third control impulses and between the third and fourth control impulses. When master close key MCK is operated, pause relay PS is energized in response to the energization of counting relays Cl and C2 so that a pause is produced between the first and second control impulses and between the second and third control impulses. When the master check key CHK is operated, pause relay PS is energized in response to the energization of counting. relays Cl, C2 and C3 so that a pause is produced between the first and second impulses, between the second and third impulses and between thethird and fourth impulses.

At the dispatchers ofllce," each pause efiected during the transmission of a code causes a time delay drop-out code receiver relay PR, which is energized while relay LX is energized, to drop out. If the code is being transmitted from the dispatchers omce, the dropping out of relay PR also efiects the deenergization of pause relay PS thereby terminating the pause and efiectins' the reenergization of relay L8 to transmit the next impulse of the code. 1

A similar pause relay P'S' is provided at the substation for producing a relatively long pause between any two of the impulses of a code transmitted from the substation. The circuit of pause relay P'S' is controlled during the transu'iission trolled by the position of the selected apparatus unit at the time the indication code is being transmitted.

At the substation, each pause eil'ected during the transmisison of a code causes a similar time delay dropout code receiver relay PR. to drop out and effect the deenergization of the associated pause relay P'S' if the code is being transmitted from the substation.

P34 are selectively energized and locked up at the dispatchers ofilce in response to the long pauses between the impulses, relay Pl2 being energized and locked up during each pause produced between the first and second impulses, relay P23 being energized and lockedup during each pause produced between the second and third impulses, and relay P34 being energized and locked up during each pause produced between the third and fourth impulses. Therefore, the energized condition of register relays M2,? and P34 at the termination of each code depends upon the code transmitted. None of these three register relays is energized during the transmission of the selection and of the selection check codes of apparatus unit AUI. Only relay P34 is energized during the transmission of the selection and of the selection check codes of apparatus unit AUZ. Only relay P23 is energized during the transmis- 45 sion of the selection and of the selection check codes of apparatus unit AU3. Only relay H2 is energized during the transmission of the selection and of the selection check codes of apparatus unit AU4.- Relays PH and P34 are ener- 50 gized during the transmission of the selection and of the selection check codes of apparatus unit AU5. Relays P23 and P34 are energized during the transmission of the tripping and of the trip indication codes. Relays PH and P23 56 are energized during the transmission of the closing and the close indication codes. 'Relays PI 2, P23 and P34 are energized during the transmission of the indication check code. A similar group of three pause register relays P'l2, P'23 U and P'34 are selectively energized and locked up at the substation in a similar manner by the pauses in the various transmitted codes.

The energization of countin relay C4 at the dispatchers ofilce in response to the fourth and last-impulse of each code transmitted from the dispatchers oflice interrupts the energizing circuit of relay LS so as to prevent it from being reenergized at the termination of the fourth im-.

pulse. The counting relay C'4 at the substation similarly prevents relay US from being reenergized at the termination of the fourth impulse of each code transmitted from the substation. Consequently, after the termination of the fourth impulse of each code, time delay dropout relays .Three code pause register relays Pl2, P23, and

PR and F8 are both deenergised tora sumcient tion code for apparatus unit AU! is transmitted,

etc. I! the selection code is transmitted from the dispatchers oillce, the selection relay is energized and locked up as soon as relay PR drops out, but

. ii the selection code is transmitted from the substation, the selection relayis not energized until atter'relay PR has effected the droppingout or its associated time delay dropout operation delay relay OD. The energization oi any selection relay Sl to SI, inclusive, eflects the energization of counting chain reset relay CR which. in turn, effacts the deenergization of sending control relay BC and or counting relays CI to Cl, inclusive,

and any 01' the register relays at the dlspatchersofllce that are energized by the selection code. Relay CR also effects the energization and locking up of operation transfer relay Tl.

When relay. P'R' drops out at the end of a selection code, it eflects the energization and locking up of one of the group selection relays S'l any or the substation register relays that are energized by the selection check code and to eflect the energization and locking up of operation transfer relay TI. When relay '1'"! is energized. master indication relays 1'0 and 1"!" are selectively controlled by the position of the selected apparatus unit so that relay PC is energized it the selected apparatus unit ls in its closed position and relay IT' is energized it the selected apparatus unit is in its open position.

When relay PR at the dispatcher's omce drops out at the end or a selection check code it eflects the energization and locking up of code check relay CH it the selection check code received at the dispatchers ofllce checks with the transmitted selection code. It the selection check code is transmitted from the dispatchers ofllce, relay CH is energized as soon as relay PR drops out, but it the selection check code is transmitted from the substation, relay OH is not energized until after relay PR has effected the dropping out of operation delay relay OD. Relay CH eflects the lightto 8'8, inclusive, depending upon the selection 7 code that has been registered by relays Pl2. P'It and PM. For examplerrelay S'l' is energized and locked up ii the selection code or apparatus unit AUI has been transmitted, relay 5'! is energized and locked up if the selection code of apparatus unit AU: has been transmitted. etc. It

the selection code is transmittedirom the substation to the dispatchers ofllce, the substation selection relay is energized as soon as relay P'R. drops out, but if the selection code is transmitted from the dispatchers oillce, the substation selection relay is not energized until after relay P'R. has effected the dropping out or its associated time delay dropout operation delay relay O'D'. The energization of any selection relay S'l to 8'', inclusive, eflects the energization of counting chain reset relay CR' which in turn deenergizes counting relays C! to (2'4, inclusive, and any of the substation register relays that are energized by the selection code. Relay C'R. also ing or the amber lamp corresponding to the selected apparatus unit, the energization of counting chain reset relay OR to reset the counting and register'relays at thedispatchers ofllce, and also the energization and locking up of operation transfer relay T2.

When relay PR at the dispatcher's omce drops.

. nation of counting chain reset relay CR to reset efiects the energization and locking up of operation transfer relay T'l at the substation. Relay T'l in turn completes a holding circuit for receiving control relay R'C', which is energized by relay Cl whenever a code is received at the substation !rom the dispatcher's omce, and also completes an energizing circuit for sending control relay S'C' which eflects the transmission or the selection check code corresponding to the selected substation selection relay from the substation to the dispatchers omce.

When substation relay P'R' drops out at the end 01' a selection check code, it eflects the energization and locking up or code check relay 0'11 1! the proper selection check code has been transmitted. It the selection check code is transmitted from the substation, relay C'H' is energized as soon as relay P'R' drops out, but it the selection check code is transmitted from the dispatchers oillce. relay C'H' is not energized until after relay P'R' has eilected the dropping out or operation delay relay O'D'. Relay C'H' in turn effects the emulation of counting chain reset relay C'R' to reset counting relays C'l to 0'4. inclusive, and

the counting and register relays at the dispatchers omce.

When relay P'R' at the substation drops out at the end of a transmitted control code, it eilects the deenerg'ization and dropping out of its associated-operation delay relay OD' which in turn eflectstheenergization of master close relay MC' if a closing code has been transmitted and the energization of 'master trip relay M'T' if a tripping code has been transmitted. When close relay M'C' is energized, it eflects the closing of the selected apparatus unit, whereas when trip relay MT' is energized, it eflects the opening of the selected apparatus unit. The selected appa ratus unit in changing its position causes its associated indication relay in a group 01. relays PA! to IA'S, inclusive, to become deenergized and change the energizatlons oi relays 1'0 and 1"!" so that they are selectively energized in accordance with the new position of the selected apparatus unit. A circuit is also completed for counting chain reset relay CR' in response to the operation of the selected apparatusunit to reset the substation counting and register relays.

When relay P'R' drops out at the end of a transmitted indication check code, it eflects the deenergization and dropping out of its associated operation delay relay O'D which'in turn effects the energlzation of counting chain reset relay C'R' to reset the counting and register relays at the substation.

After the counting and register relays at the substation have been reset at the end oi a control or indication check code, sending control relay S'C' is reenergized and locked up to eflect the transmission of an indication code corresponding to the position of the selected apparatus unit.

When substation relay PR drops out at the end of an indication code, it efl'ects the reenergization or the indication relay associated with the selected apparatus unit and also eil'ects the energization of counting chain reset relay C'R' to reset the substation counting and register relays.

When relay-PR at the dispatchers oilice drops out at the end of the transmission of an indication code, it effects the deenergization and dropping out of its associated operation delay relay OD which in turn efiects the energization of master indication close relay MC if a close indigroup IRl to IRS, inclusive, which is individual go to the selected apparatus unit so that the indicating lamps individual to the selected apparatus unit are lighted to indicate that it is in its open position.

The operation of an indication relay in relay group IRI to IRS, inclusive, in response to an indication code effects the energization of counting chain reset relay CR to reset the counting and register relays at the dispatchers ofllce.

For restoring the supervisory equipment after a selection has been-made, lockout relay LO at the dispatchers oflice is arranged to be energized in response to an operated select key beingrestored to its normal position. Lockout relay L is also arranged to be energized in response to the operation of emergency reset key EMK by the dispatcher. Lockout relay L0 when energized is arranged to effect the transmission of a single reset impulse over line conductors LI and L2. This single reset impulse causes release relay RL at the dispatchers ofllce to operate and reset the apparatus unit thereat to its normal-at-rest position and to operate release relay R'L' at the substation to reset the apparatus unit thereat to its normal-at-rest position.

At the substation, start relay S'T' is arranged to be energized and locked up in response to any one of the apparatus units thereat changing its position and effecting the deenergization of its associated indication relay while the supervisory equipment is in its normal-at-rest position. When energized, start relay S'T' causes a selection code corresponding to the apparatus unit which has changed its position to be transmitted from the substation to the dispatcher's oflice. This selection code eiTects at the substation and at the dispatchers ofilce the energization and locking up of the selection relays individual to the apparatus unit which has changed its position.

The first impulse of the selection code received at the dispatchers oillce from the substation also effects the deenergization of bell relay BR so "that circuits are completed for alarm bell AB position occupied by the operated apparatus unit. Q

Also, the indication code effects at the substation the energization and locking up of the indication relay individual to the operated apparatus unit. At the termination of the indication code, a single reset impulse is transmitted from the dispatcher's oilice to the substation to restore the supervisory apparatus at the two stations to its normal-atrest position.

Relay BR will remain deenergized with the bell ringing and alarm lamp AL lighted until the dispatcher presses emergency reset key EMK. Key EMK energizes relay BR, thereby silencing the bell, extinguishing alarm lamp AL and lighting start lamp STL.

The unit whose indication was changed by the automatic operation will be marked by the white disagreement lamp until acknowledged by the dispatcher turning the corresponding disagreement key to the new position.

A detailed description of the operation of the embodiment of my invention shown in the drawings is as follows: When the equipment is not in use, each group of lamps is lighted to indicate the position of the corresponding apparatus unit. For the purpose of this description, it will be assumed that each of the apparatus units in the substation is in its open position so that its associated green lamp in the dispatchers oilice is lighted through a circuit including contacts b 01' the associated indicating relay and contacts d of the associated disagreement key. For example, the circuit of green lamp G2 includes contacts b 01 indicating relay m2 and contacts (1 of disagreement key DKI.

when the supervisory equipment at both stations is in its normal-at-rest position, bell ring-- its open position, the energizing circuit oi'each of the associated indicating relays at the substation is completed through auxiliary contacts b of the apparatus unit and-the lower winding and contacts a of the associated indicating relay. For example, the circuit of indicating relay I'A'2 is 56 completed through the lower winding of this relay, contacts a of relay I'A'Z and auxiliary contacts b of apparatus unit A-U2.

When the equipment is in its normal-at-rest position, a circuit is also completed for start lamp 60 STL through contacts b of relay LX, contacts (I of relay Ci, conductor 300, contacts b of select key SKI, contacts b of select key SK2, contacts b of select key 8K3, contacts b of select key SKI, contacts b oi /select key SK5, conductor I00, con- 55 tacts ,f of start relay ST, conductor 200 and contacts c of relay BR.

It will now be assumed that the dispatcher desires to select and operate apparatus unit AU! at the substation. After first observing that start lamp STL is lighted, the operator moves select key SK2 from the position shown in the drawing to its other position and then moves disagreement key DK2 to its other position. The opening of contacts d and the closing of contacts 0 of dis- 76 agreement key DK2 effect the connection of white aseavee 11 lamp W2 in series with green lamp G2 so that both of these lamps are lighted.

The opening of contacts b of select key 882 opens the above traced circuit for start lamp BTL.

The closing of contacts a of select key 8K2 completes an energizing circuit for start relay BT through conductor 222, contacts h of relay Ti, contacts d of relay RC. conductor 2", contacts a of select key 8K2, contacts b of select key SKI, conductor 200, contacts at of relay'Ci and contacts b of relay LX. By closing itscontacts 0. start relay ST completes a locking circuit foritself through contacts h of relay RL. The closing of contacts a of start relay BT completes an energizing circuit for sending relay SC through conductor 20 I, contacts a of start relay ST, conductor 202, contacts I of relay Tl, contacts I of relay T2. contacts b of relay Cl, conductor 202 and contacts b of relay CR. The closing of contacts e of relay SC completes a locking circuit for this relay through conductor I02 and contacts b of relay CE.

The closing of contacts of relay SC completes an energizing circuit for line impulse sender relay through contacts b of relay PS. contacts d of relay Lx, conductor "2, contacts b of relay RL, conductor 2, contacts c of relay SC, conductor contacts d of relay CR, conductor 202 and contacts I of relay C4. The closing of contacts a of relay LS connects the positive terminal of battery BAT to line conductor LI and the closing of contacts c of relay LS connects the negative terminal of battery BAT to line conductor L2 so that a positive impulse is transmitted over the line conductors. At the dispatchers omce, this impulse picks up line relay LR, which by closing its contacts a completes an energizing circuit for auxiliary line relay mi. The closing of contacts a of relay L! completes an energizing circuit for code pause receiver relay PR. The closing of contacts a of relay PR completes a holding circuit for relay OD so that this relay does not become deenergized when relay Cl opens its contact I; The closing of contacts a of relay Lx also completes an energizing circuit for counting relay Cl through contacts b of relay CT and contacts b of relay C2. The closing of contacts a of relay CI completes a locking circuit for this relay through conductor 202 and contacts b of relay CR and a locking circuit for relay PR. through contacts b of relay CT, contacts b of relay C2, contacts a of relay Cl, conductor "2 and contacts b of relay CR.

The opening of contacts d of relay 1.x interrupts the heretofore described circuit for line impulse sender relay LS so that it opens its contacts a and c to remove the impulse from line conductors LI and L2 thereby eifecting the successive deenergization of the relays LR. and 1.x. The closing of contacts b of relay 1.x completes an energizing circuit for counting chain transfer relay CT through contacts e of relay Cl, contacts I of relay C2 and contacts h of relay C4. The closing of contacts c of relay CT completes a shunt circuit around contacts b of relay LX so as to complete a locking circuit for relay CT. The opening of contacts b of relay CT interrupts the locking circuit of relay PR, but due to the fact that this relay is a time delayed dropout relay,

it remains in its energized position for a predetermined time after its energizing circuit is interrupted.

The closing of contacts d of the relay 1.x reestablishes the heretofore described energizing circuit for relay LS so that it again connects line conductors LI and L2 to the battery BAT so as to cause another impulse to be transmitted over these line conductors.

The second impulse to be transmitted over line 5 conductors Li and L2 eiIects the energization of relays LR and 1.x, and the closing of contacts a of relay 1.x reenergizes relay PR. before it has had time to be restored to itslnormally deenergized position. The closing of contacts a of relay LX also completes an energizing circuit for chain relay C2 through contacts b of relay Cl and contacts a of relay CI. The closing of contacts a of relay C2 completes a locking circuit for this relay through conductor "2 and contacts b of relay CR and also a locking circuit for relay PR through contacts a. of relay CI, contacts b of relay CI, contacts a, of relay C2, conductor 202 and contacts b of relay CR. The opening of contacts d of relay 1.x again interrupts the energizing circuit of relay LS so as to terminate the impulse being sent over line conductors Li and L2 and.

deenergize relays LR and 1.1:. The opening of contacts c of relay 1.x, which contacts are connected in parallel with the series connected contacts h of relay C4 and I of relay C2 in the heretofore described energizing circuit of relay CT, interrupts the holding circuit of relay CT so that this relay becomes deenergized. The opening of contacts a of relay CT interrupts the holding circuit of relay PR.

The closing of contacts :1 of relay Lx again reestablishes the energizing circuit of relay LB so that a third impulse is transmitted over line conductors LI and L2, and this third impulse effects the energization of relays LR and Lx in the same manner asthe two previous impulses. The closing of contacts a of relay Lx again reestablishes the energizing circuit of relay PR. before this relay can drop out and also completes an energizing circuit for counting relay C2 through contacts d of relay Cl, contacts c of relay C2 and contacts b of relay CT. The closing of contacts a of relay CI completes a locking circuit for this relay through conductor "2 and contacts b of 5 relay CR and also completes a locking circuit for relay PR. through contacts b of relay CT, contacts c of relay C2, contacts d of relay C4, contacts a oi relay CI, conductor 2 and contacts b of relay CR. The closing of contacts i of relay C3 completes an energizing circuit for code pause sender relay PB through conductor 3", contacts b of relay DO, conductor 2, contacts c of relay PR, conductor "1, contacts i of relay C3, contacts b of relay CH, conductor 3, contacts i of relay 5T, conductor 2", contacts 0 of select key 882, conductor III, contacts I of relay P23, conductor 2", contacts I of relay Pl2, conductor 3M, contacts a of relay OD. contacts b of relay C4, contacts 9 of relay Cl, conductor "2 and coneo tacts b of relay CR.

The opening of contacts :1 of relay Lx again interrupts the energizing circuit of relay is so as to terminate the third impulse and cause relays LR and L to become deenergized. The

66 closing of contacts d of relay Lx does not re- 70 cuit for relay CT through contacts I: of relay Cl,

contacts a of relay CI and contacts a of relay CI. The closing of contacts c of relay CT shunts contacts b of relay LX so as to complete a loc circuit for relay CT.

7s The opening of contacts b of relay CI intersome rupts the locking circuit of relay PR, and since the circuit of relay L8 is still open at contacts b of relay PS, relay PR remains deenergized for a sufficient time to drop out and close its contacts d, thereby completing an energizing circuit for code register relay P34 through conductor 201, contacts e of relay C3, contacts b of relay PR, contacts a of relay OD, contacts b of .relay C4, contacts a of relay Cl, conductor 302 and contacts b of relay CR. -The closing of contacts a of relay P34 completes a locking circuit for this relay through conductor 302 and contacts 17 of relay CR.

The opening of contacts of relay PR interrupts the heretofore described energizing circuit for relay PS so that is closes its contacts b and reestablishes the heretofore described energizing circuit for relay LS so that a fourth impulse is transmitted over line conductors LI and L2, and this fourth impulse effects the energization of relays LR and LX in the same manner as the three previous impulses. The closing of contacts a of relay LX again reestablishes the energization of relay PR so that it is again picked up.

The closing of contacts a of relay LX also completes an-energlzing circuit for counting relay C4 through contacts 0 of relay C3 and contacts a of relay CT; The closing of contacts a of relay C4 completes a locking circuit for this relay through conductor 302 and contacts b of relay CR and also a locking circuit for relay PR through contacts a of relay CT, contacts 0 of relay C3, contacts a of relay C4, conductor 302 and contacts b of relay CR. p

The opening of contacts at of relay LX again interrupts the energizing circuit of relay LS so as to terminate the fourth impulse and cause relays LR and LX to becomedeenergized. The opening of contacts 0 of relay LX, which contacts are connected in parallel with the series connected contacts h of relay C4 and contacts 9 of relay C3 in the heretofore described energizing circuit of relay CT, interrupts the circuit of re-' lay CT so that this relay becomes deenergized and at its contacts a interrupts the locking circuit of relay PR. The closing of contacts d of relay LX does not reestablish the heretofore described energizing circuit of relay LS because this circuit is now open at contacts I of relay C4. Consequently, contacts a of relay LX remain open long enough to allow relay PR to drop out and complete an energizing circuit for, selection point relay S2 through conductor I04, contacts e of relay P34, contacts d of relay P23, contacts b of relay Pl2, conductor 208, contacts b of relay T2, contacts i of relay C4, contacts a of relay SC, contacts d of relay PR, contacts 7 of relay Tl, conductor 3 and contacts 7' of relay RL.

The closing of contacts 0 of relay S2 completes a locking circuit for this relay through conductor 3 and contacts 7" of relay RL. The closing of contacts i of relay S2 completes an energizing circuit for counting chain reset relay CR through contacts I of relay 1R2, conductor I05, contacts b of relay MT, conductor 209, contacts d of relay o TI and conductor 320. The opening .of contacts 17 of relay CR interrupts the heretofore described locking circuits for relays Cl, C2, C3, C4, P34

and SC so that these relays are-restored to their F normal deenergized positions. The closing of contacts I of relay Cl reestablishes the heretofore described energizing circuit for relay OD. The closing of contacts a of relay CR completes an energizing circuit for relay Tl through contacts f of relay RL, conductor 2 l0 and contacts b a conductor 402 and contacts e of relay C'l.

oi relay CH. The closing of contacts a of relay Tl completes a locking circuit for this relay through conductor II I and contacts 1 of relay RL. The opening of contacts (1 of relay Tl interrupts the heretofore described energizing circuit of relay CR. Therefore, at the end of the selection code, relays ST, TI, 82,, 0D and BR at the dispatchers ofiice are energized.

While the selection impulses are effecting the heretofore described operations at the dispatchers ofiice, they are also eflecting the following operations at the substation: The first impulse transmitted over line conductors LI and L2 effects the energization of relay UK, which by closing its contacts a completes an energizing circuit for relay UK. The closing of contacts a of relay L'X' completes an energizing circuit for code pause receiver relay PR'. The closing of contacts a of relayP'R' completes a holding circuit for relay O'D' so that this relay does not become deenergized when relay C'l opens its contacts d. The closing of contacts a of relay L'X' also completes an energizing circuit for counting relay C'i through contacts b of relay C'2 and contacts I) of relay C'T'. The closing of contacts a of relay C'l completes a locking circuit for this relay through conductor 400 and contacts b of relay C'R' and also a locking circuit for relay PR through contacts b of relay C'T'. contacts b of relay C'2, contacts a of relay C'l, conductor 400 and contacts b of relay C'R'.

At the termination of the first impulse, relay L'R' opens its contacts a and effects the deenerglzation of relay UK. The closing of contacts d of relay LX' completes an energizing circuit for relay CT' through contacts k of relay C'l, contacts I of relay C'2 and contacts 71. of relay C'4. The closingof contacts 0 of relay C'T' completes a shunt circuit around contacts d of relay UK so as to complete a locking circuit for relay C'T'. The closing of contacts e of relay C'T' completes an energizing circuit for relay RC' through conductor i00,contacts e of relay CT, conductor 40!, contacts b of relay S'C',

closing of contacts i of relay RC' completes a shunt circuit around contacts e of relay CT' in the energizing circuit of relay RC'. The opening of contacts b of relay C'T' interrupts the heretofore described locking circuit of relay P'R', but due to the fact that this relay is a time delayed dropout relay, it remains in its energized position for a predetermined time after its energizing circuit is interrupted.

The second impulse of the selection code eifects the energization of the relays L'R' and UK in the same manner as the first impulse, and the closing of contacts a of relay L'X' reenergizes relay PfR before it has had time to be restored to its normally deenergized position. The closin of contacts a of relay L'X' also completes an energizing circuit for chain relay C'2 through contacts d of relay 0'3 and contacts a of relay C'T'. The closing of contacts a of relay C'2 completes a locking circuit for this relay through conductor 400 and contacts bof relay C'R' and also a locking circuit for relay P'R' through contacts a of relay CT, contacts a of relay C'2, conductor 400 and contacts b of relay C'R'. I

At the termination of the second impulse, relays L'R' and UK are again deenergized and the opening of contacts c of relay UK, which contacts are connected in parallel with the series connected contacts I of relay C'2 and contacts h. of relay C'4 in the heretofore describedener- 15 gizing circuit of relay CT', interrupts the holding circuit of this relay so that it becomes deenergized. The opening of contacts a of relay CT interrupts the heretofore described locking circuit for relay P'R'.

When the third impulse is transmitted over line conductors LI and L2, relays L'R and UK are again energized. The closing of contacts a of LX' i'eestablishes the. energizing circuit of relay PR' before this relay can drop out and also completes an energizing circuit for counting relay '3 through contacts d of relay C4, contacts c of relay C! and contacts b of relay CT. The closing of contacts a of relay 0', completes a locking circuit for this relay through conductor 400 and contacts b of relay C'R' and also completes a locking circuit for relay P'R' through contacts b of relay C'T', contacts 0 of relay C'2, contacts d of relay 0'4, contacts a of relay 0'3, conductor 400 and contacts b of relay C'R.

At the end of the third impulse, relays L'R' and UK are again deenergized, and the closing of contacts d of relay L'X reestablishes another circuit for relay C'T through contacts 70 of relay C'I, contacts a of relay C! and contacts h of relay C'4. The closing of contacts 0 of relay C'T' reestablishes the holding circuit for this relay around contacts d of relay UK, and the opening of contacts b of relay CT' interrupts the locking circuit of relay P'R'.

Since between the third and fourth impulses there is a long pause due to the energization of code pause sender relay PS at the dispatcher's oillce, contacts a of relay L'X' remain open for a suihcient length of time to allow time relay PR' to drop out. The closing of contacts b of relay P'R' completes an energizing circuit for relay P'34 through conductor 50L contacts e of relay C3, contacts b of relay P'R', contacts b of relay L'O, contacts a of relay O'D', contacts b of relay C4, contacts 0 of relay Cl, conductor 400 and contacts b of relay CH. The closing of contacts a of relay P'Il completes a locking circuit for this relay through conductor 400 and contacts b of relay C'R'.

The fourth impulse effects the energization of the relays L'R' and UK in the same manner as the previous impulses, and the closing of contacts a of relay L'X' reestablishes the energizing circuit of relay P'R' so that this relay again picks up. The closing of contacts a of relay L'X also completes an energizing circuit for counting relay C'4 through contacts c of relay 0'3 and contacts a of relay CT. The closing of contacts a of relay 0'4 completes a locking circuit for this relay through conductor 400 and contacts b of relay C'R' and also a locking circuit for relay PR through contacts a of relay C'T', contacts 0 of relay C3, contacts a of relay C'4, conductor 400 and contacts b of relay C'R'.

At the termination of the fourth impulse, relays LR. and UK are again deenergized. The opening of contacts 0 of relay UK, which contacts are connected in parallel with the series connected contacts g of relay 0'3 and contacts h of relay C4 in the heretofore described energizing circuit for relay C'T', interrupts the holding circuit of this relay so that it becomes deenergized. A predetermined time after contacts a of relay C'T' are opened, relay P'R' drops out and opens its contacts a in the holding circuit of relay O'D'. After being deenergized for a predetermined time interval, relay O'D' also drops out and by closing its contacts I completes an en-- ergizing circuit for relay S: through conductor 000, contacts e of relay P'Il, contacts d of relay 1'', contacts b of relay P'l2, conductor 502, contacts 11 of relay T'2, contacts 1 of relay C'4. contacts I of relay O'D', contacts d of relay PR, conductor 404, contacts h of relay T'l, conductor 503 and contacts h of relay R'L'. The closing of contacts a of relay 8': completes a locking circuit for this relay through conductor 403, contacts I of relay L'O, conductor 003 and contacts h of relay R'L'. The closing of contacts e of relay S'! completes an energizing circuit for relays 1'0 and IT in series through conductor 603. The closing of contacts a of relay I'T' completes an energizing circuit for relay C'R' through contact b of relay R'L', conductor 426, contacts a of relay IT', contacts b of relay TI and conductor 50!. The opening of contacts b of relay C'R' interrupts the heretofore described holding circuits of the relays C! to 0'4, inclusive, and PS4. The closing of contacts d of rela C'l reestablishes the original energizing circuit for relay O'D'. The closing of contacts a of relay C R completes an energizing circuit for relay T'I through conductor 506, contacts d of relay R L, contacts 11 of relay L'O, contacts I of relay C'H' and conductor 401. The closing of contacts c of relay T'l completes a locking circuit for itself through conductor 403, contacts 1 of relay L'O, conductor I03 and contacts h of relay RL'. The closing of contacts a of relay T'l completes a holding circuit for relay RC' through contacts )2. of relay R'L', conductor 503, contact q of relay T'l, conductor 402, contacts b of relay S'C', conductor 40l and contacts 1' of relay R'C'. The opening of contacts b of relay T'l interrupts the heretofore described energizing circuit of relay CR'.

Therefore, at the end of the selection code, relays R'C', T'l, S'LI'C', I'T', O'D', and I'A'I to I'A'i, inclusive, are energized, and the substation is now ready to transmit a selection check code to the dispatchers ofllce. This selection check: code is the same as the selection code; namely, four positive impulses with a pause between the third and fourth impulses.

The closing of contacts a of relay T'l completes an energizing circuit for the relay S'C' through contacts h of relay L'O, conductor 408, contacts a of relay R'C', contacts a of relay T' I, conductor contacts d of relay T'2, contacts b of relay Cl, conductor 400 and contacts b of relay C'R'. The closing of contacts 0 of relay S'G' completes a locking circuit for this relay through contacts h of relay L'O, conductor 408, contacts 0 of relay S'C', conductor 400 and contacts b of relay C'R'. The opening of contacts b of relay S'C' interrupts the heretofore described holding circuit for relay R'C'. The closing of contacts e of relay SC' completes an energizing circuit for relay US through contacts b of relay P'S', contacts b of relay L'X', conductor 4", contacts e of relay S'C', contacts I of relay 0'4, conductor 0 and contacts d of relay C'R'. The closing of contacts a of relay L'S' connects the positive terminal of battery B'A'T' to line conductor Li, and the closing of contacts 0 of relay L'S' connects the negative terminal of battery B'A'T' to line conductor L2 so that the first positive impulse of the selection check code is transmitted over the line conductors.

At the substation, this impulse picks up relay L'R', which by closing its contacts a com- 5 closing of contacts a of relay LX' completes pletes the energizing circuit of relay UK. The

'L B so as to assures a the energizing circuit for relay P'R' which in turn reestablishes the holding circuit for relay O'D' so that this relay does not become deenergized when relay C'l opens its contacts (I. The closing of contacts a of relay US also completes the heretofore described energizing circuit for counting relay C'l, which by closing its contacts a completes'the heretofore described locking circuits for itself and for relay PR'.

The opening of contacts 11 of relay UK interrupts the heretofore described circuit for relay US so that it opens its contacts a and c to remove the impulse from line conductors LI and L2, thereby effecting the deenergization of relays HR and UK. The closing of contacts of of relay L'x' completes the energizing circuit for relay T' through contacts is of relay 0'i. contacts I of relay 0'2 and contacts is of relay 0'4. The closing of contacts c of relay 0'T' completes a shunt circuit around contacts (I of relay UK in the energizing circuit for relay C'T'. The opening of contacts b of relay 0"!" interrupts the locking circuit for relay P'R'. but due to the fact that this is a time delay dropout relay, it remains in its energized position for a predetermined time after its energizing circuit is interrupted.

The closing of contacts b of relay LX' reestablishes the energizing circuit of relay US so that it again connects line conductors LI and L! to battery B'A'T' and causes the second impulse of the selection check code to be transmitted over these line conductors. N

This second impulse effects the energization of relays L'R. and UK. and the closing of contacts a of relay L'x' reenergius relay P'R before it has had time to be restored to its normally deenergized position. The closing of contacts a of relay L'x' also completes the energizing circuit for relay 0'! through contacts d of relay 0! and contacts a of relay 0'T'. The closing of contacts a of relay 0'! completes the heretofore described locking circuits for this relay and relay P'R' through conductor 4" and contacts b of relay 0' It. The opening of contacts I: of relay L'X' again interrupts the energizing circuit of relay terminate the second impulse and effect the deenergization of relays U3 and UK. The opening of contacts c of relay L x'. which contacts are connected in parallel with series connected contacts I of relay 0! and contacts is of relay 0'4 in the heretofore described energizing circuit of relay 0'T, interrupts the holding circuit of this relay so that it becomes deenergized. The opening-of contacts a of relay 0' T interrupts the holding circuit of relay P'R.

The closing of contacts b of relay L'x' again reestablishes the energizing circuit of relay US so that the third impulse of the selection check code is transmitted over line conductors Li and L2, and this third impulse effects the energization of relays U3 and UK in the same manner as the two previous impulses. The closing of contacts a of relay L'x' again reestablishes the energizing circuit of relay P'R' before this relay can drop out and also completes the energizing circuit for relay 0'! through contacts d of relay 0'4, contacts c of relay 0'! and contacts b of relay UT. The closing of contacts a of relay 0'! completes the heretofore described locking circuit for this relay and relay P'R' through conductor 4" and contacts is of relay 0'8.

The closing of contacts 1 of relay 0'. completes an energizing circuit for relay P'B' through contacts c of relay P'R', contacts i of relay 0", con- 8'0, contacts I of relay 0'4, conductor 4i. and

contacts d of relay 0' R.

The opening of contacts b of relay L'x' interrupts the energizing circuit of relay L 8" so as to terminate the third impulse and causes relays L'R' and UK to become deenergized. The closing of contacts b of relay L'x' does not reestablish' the heretofore described energizing circuit of relay US because this circuit is now open at contacts I) of relay PB'. The closing of contacts 4 of relay L'X' completes an energizing circuit for relay 0"!" through contacts k of relay 0'l. contacts a of relay 0'! and contacts In of relay 0'4. The closing of contacts 0 of relay 0T' shunts contacted of relay UK so as to complete a locking circuit for relay C'T'.

The opening of contacts I: of relay 0'T' deenergizes the relay P'R', which after being deenergized for a predetermined time opens its contacts a and interrupts the holding circuit for relay O'D'. Before time relay OD' drops out, a circuit is completed for relay P'I4 through conductor Ill, contacts e of relay 0'3, contacts I: of relay P'R', contacts 2: of relay U0 and contacts a of relay O'D'. contacts I: of relay 0'4, contacts c of relay C'i, conductor 4" and contacts b of relay 0'8. The closing of contacts a of relay P' completes a locking circuit for this relay through conductor 4" and contacts b of relay 0'R'. The opening of contacts 0 of relay P'R' interrupts the heretofore described energizing circuit of relay P'B so that the closing of its contacts b reestablishes the liegetofore described energizing circuit for relay The energization of relay L'B' causes the fourth impulse of the selection checkcode to be transmitted over line conductors LI and, L2, and this fourth impulse effects the energi'zation of relays L'R" and UK in the same manner as the three previous impulses. The closing of contacts a of relay L'x again reestablishes the energization of relay P'R' so that it again picks up and reenergizes relay O'D' before it drops out. The closing of contofore described locking circuits for this relay and tacts a of relay 11'! also completes an energizing circuit for counting relay 0'4 through contacts 0 of relay 0'! and contacts a of relay 0'T'. The closing of contacts a of relay 0'4 completes the hererelay P'R' through conductor 4 and contacts b of relayC'R'.

The opening of contacts in of relay we again interrupts the circuit of relay US so as to terss minate the fourth impulse and cause relays L'R and UK to become deenergized. The opening of contacts 0 of relay UK, which contacts are connected in parallel with the series connected contacts a of relay 0! and contacts h of relay 0'4 in the heretofore described energizing circuit of relay C'T', interrupts the circuit of relay 0'T' so that this relay becomes deenergized. and by opening its contacts a, deenergizes relay P'R'. The closing of contacts b of relay L'X' does not reestablish the heretofore described energizing circuit of relay US because this circuit is now open at contacts! of relay 0'4. Consequently, contacts a of relay Lx remain open long enough to allow relay PR. to drop out. If the proper check code has been transmitted. an energizing circuit for code check relay CH' is completed through conductor 4", contacts c of relay T'l, conductor 404. contacts d of relay P'R', contacts a of relay 8'0, contacts i of relay 0'4, contacts b 15 of relay 'r's, conductor 40!. contacts b of relay P'l2, contacted of relay P'2l, contacts a of relay P'Il, conductor I", contacts a of relay 8'2, conductor "3. contacts I of relay LO', conductor I03 and contacts 7: of relay R'L'.

The closing of contacts I: of relay C'H' completes a locking circuit for this relay through conductor I, contacts I of relay L'O, conductor I03 and contacts hot relay RL'. The closing of contacts a of relay C'H' completes an energizing circult for relay ,C'R' through contacts I of relay 1o T'2 and conductor Ill. The opening of contacts b of relay C'R'. interrupts the heretofore described locking circuits for relays C'l to 0', inclusive P'llandS'C'. The closing of contacts d of relay C"-I fiestablishes the energizing circuit oiftacts i of relay C H. By 80 of relay T'2 interrupts the heretofore described energizing circuit for relay C'R', and the closing of contacts a of relay T'.2 completes a shunt circuit around the winding of relay I'C' through conductor II 1, contacts e of relay T'2 conductor l2, contacts a ofrelay 8'2 and contacts b of apparatus unit AU2. Consequently relay I'C' drops out and relay I'T' remains energized.

At the termination of the selection check code, relays 82, C'H', T'l. T'2, I'T', O'D', and I'A'l to I'A'I, inclusive, are energized at the substation. v

The four impulsesof ,the selection check code effect the same operation of the relays LR, 1.x, CI to C4, inclusive, CT, PR, 0D and P at the dispatchers oillce as the impulses of the selection code did, except that the energization of relay CT at the end of the first impulse of a selection check code completes an energizing circuit for relay RC through contacts e of relay CT, contacts b of relay SC, conductor ill and contacts 1 of relay RL. This circuit for relay RC was not completed during the transmission of the selection code because the contacts b of relay SC were then open. By closing its contact i, relay RC completes a locking circuit for itself by shunting contacts e of relay CT.

At the termination of the fourth impulse of the selection check, code, time delay relays PR and 0D successively become deenergized and drop out, If the correct selection code is received by the apparatus at the dispatchers ofllce, the closing of contacts b of relay 0D completes an energizing circuit for relay CH through contacts e of relay Tl, contacts d of relay PR, contacts b of relay 0D, contacts i of relay C4, contacts b of relay T2, conductor 208, contacts b of relay Pl2, contacts d of relay P23, contacts e of relay P34, conductor contacts 0 of relay S2, conductor 2 and contacts 1 of relay RL. The closing of contacts i of relay CH completes a locking circuit for this relay through conductor 2 and contacts 1 of relay RL. The closing of contacts c of relay CH completes a circuit for amber lamp A2 through conductor 2l2 and contacts a of relay S2. The lighting of amber lamp A2 informs the dispatcher that apparatus unit AU2 at the substation has been properly selected. The closing of contacts a of relay CH completes an energizing circuit for relay CR through contacts d of relay T2, contacts a of relay TI and conductor 320. The open- 76 it drops out and by closing its contacts b reing of contacts b of relay CR interrupts the looking circuits of relays CI to C4, inclusive, and PM so that these relays become deenergized. The closing of contacts I of relay Cl reestablishes the energizing circuit of relay OD. The closing of contacts a of relay CR completes an energizing circuit for relay T2 through contacts! of relay RL, conductor 2|. and contacts k of relay CH. The closing of contacts e of relay T2 completes a locking circuit for this relay through conductor Ill and contactai of relay RL. The opening of contacts at of relay T2 interrupts the heretofore described circuit for relay CR.

Therefore, at the termination of the selection check code, relays ST, 82, CH, Tl, T2, RC, OD and BR are energized at the dispatchers oi'flce.

It will now be assumed that the dispatcher desires to close the selected apparatus unit AU2 and therefore momentarily operates the r'naster close key MCK. The closing of contacts a of key MCK completes an energizing circuit for the upper winding of relay MC through conductor 2| I, contacts e of relay RC, contacts 0 of relay T2, contacts b of relay Cl, conductor "2 and contacts b a locking circuit for itself and the upper winding of relay MC through conductors 3M and 302 and contacts b of relay CR. The opening of contacts b of relay SC interrupts the heretofore described locking circuit for relay RC, and the closing of contacts 0 reestablishes the heretofore described energizing circuit for relay LS. I Relays LS and LX then operate in the manner heretofore described to transmit the closing code of four, impulses in the same manner that the four impulses of the selection code were transmitted, except that in the case of the closing code a pause occurs between the first and second impulses and between the second and third impulses.

At the dispatchers ofllce, the four impulses of the closing code effect the operation of relays LX,

40 CI to Cl, inclusive, CI, 0D and PR in the same manner as the four impulses of the selection code. The energization of relay CI in response to the first impulse of the closing code, however, completes an energizing circuit for the pause relay PS through conductor 30', contacts b of relay L0, conductor 2, contacts c of relay PR, conductor 301, contacts I of relay C3, contacts h of relay C2 contacts ,1 of relay Cl, contacts m of relay CH, conductor 3, contacts 0 and e of relay 65 MC, conductor ill, wntacts a of relay 0D, contacts b of relay Cl, contacts a of relay Cl, conductor! and contacts b of relay CR. The opening of contacts b of relay PB prevents LS from being reenergized when relayLX closes its contacts dat the termination of the first impulse.

' through conductor, 2l2, contacts 0 of relay Cl,

contacts d of relay C2, contacts :1 of relay C3, contacts b of relay PR, conductor 3H1, contacts a'of relay OD, contacts b of relay 04, contacts g of relay Cl, conductor 202 and contacts b of 7 relay CR. The closing of contacts a of relay Pl2 completes a locking circuit for this relay through conductor "2 and contacts b of relay CR. The

. opening of contacts 0 of relay PR interrupts the heretofore described circuit for relay PS so that 21 establishes the energizing circuit oi relay L8 to ciiect the transmission oi the second impulse oi the closing code.

When relay C! is energized in response to the second impulse. its contacts 17 complete an energizing circuit ior the pause relay PB through conductor 800. contacts b oi relay LO. conductor 204. contacts c oi relay PR. conductor "1. contacts oi relay CI, contacts a oi relay conductor lil. contacts a of relay CH. conductor liil. contacts a oi relay OD. contacts b oi relay Cl, contacts g oi relay Cl. conductor Ill! and contacts b oi relay OR. The opening oi contacts I: oi relay PB again prevents relay L8 irom being reenergized when relay Lx closes its contacts dat the termination oi the second impulse. Consequently. time relay PR drops out aiter the second impulse has been terminated ior a predetermined time and by closing its contacts b completes an energizing circuit ior code register relay PI! through conductor lll. contacts e 01, relay CI. contacts d oi relay Cl. contacts I; oi relayPFt. conductor lit. contacts a oi relay OD, contacts b oi relay Cl. contacts a oi relay Ci. conductor 30! and contacts I; oi relay CE. The closing oi contacts a oi relay PM completes a locking circuit ior this relay through conductor ill! and contacts b of relay CR.

The opening oi contacts 0 oi relay PR interrupts the heretoiore described circuit ior pause relay PS so that by closing its contacts b it reestablishes the energizing circuit oi relay L8 to eiiect the transmission oi the third impulse oi the closing code.

The opening oi contacts oi relay C4, when it is energized in response to the iourth impulse oi the closing code. interrupts the energizing circuit oi relay LS so that this relay remains deenergized aiter the termination oi the iourth impulse. Consequently, time relay PR drops out and by closing its contacts d completes an energizing circuit ior relay CR through conductor 820, contacts b oi relay RC. contacts a oi relay T2. contacts i oi relay C4. contacts a oi relay SC. contacts d of relay PR, contacts e oi relay Tl, contacts i oi relay CH, conductor ill and contacts 1 oi relay RL. The opening oi contacts b oi relay CR interrupts the locking circuits ior relays CI to C4, inclusive, Pl I. P23, MC and SC. The opening oi contacts i oi relay C4 interrupts the heretoiore described energizing circuit ior relay CR. and the closing oi contacts 1 oi relay Ci reestablishes the heretoiore described energizing circuit ior relay OD.

Therefore. at the end oi the closing code, relays 82. CH, Ti. T2, OD and BB at the dispatcher's office are energized.

At the substation, the iour impulses oi the closing code effect the operation oi relays L'X'. C'l to 0'4, inclusive, C'T', R'C'. OD and P'R' in the same manner as the iour impulses oi the selection code. The pause between the first and second impulses is oi suiilcient duration to allow relay P'R. to drop out and close its contacts b, thereby completing an energizing circuit ior code register relay Pl! through conductor m, contacts g of relay C'i, contacts d oi relay C'!, contacts I oi relay C'I. contacts b oi relay P'R', contacts I; oi relay L'O'. contacts a oi relay O'D', contacts b oi relay 0', contacts c oi relay C'l, conductor lilii'and contacts b of relay C'R'. By closing its contacts a, relay P'l! completes a locking circuit ior itseli through conductor 0 and contacts b of relay C'R'.

The pause between the second and third impulses oi the sending code-again causes relay P'R. to drop out, and the closing oi its contacts 2: completes an energizing circuit ior code register relay P'fl through conductor III. contacts e oi relay C!. contacts I oi relay C'l. contacts b oi relay P'R, contacts b oi relay L'O. contacts a oi relay O'D'. contacts b oi relay c's. contacts 0 oi relay C'l, conductor 0 and contacts b oi relay OR. By closing its contacts a. relay P'!l completes a locking circuit ior itseli through conductor 400 and contacts b oi relay C'R'.

At the termination oi .the iourth and last impulse oi the closing code. relay PR is again deenergized. By opening its contacts a. it eiiects the deenergization oi relay O'D', which aiter being deenergized ior a predetermined time closes its contacts 1 and completes an energizing circuit ior the master close relay M'C' through contacts h oi relay PM. contacts e oi relay P'il. contacts e oi relay P'Il, conductor II. contacts a oi relay T'!. contacts i of relay C'l, contacts. b oi relay O'D', contacts a oi relay P'R', conductor 4, contacts e oi relay Ti. conductor I. contacts lc oi relay C'H, conductor 40!. contacts I oi relay L'O', conductor 803 and contact )1 oi relay R'L'. The closing oi contacts 0 oi relay M'C' completes an energizing circuit ior the closing winding CC oi apparatus unit AU! through contacts e oi relay R'C'. conductor Bis, contacts a oi relay C'l. conductor Ill, contacts e oi relay M'C'. conductor l1 and contacts is oi relay S'!.

The closing oi apparatus unit AU! opens its auxiliary contacts is and closes its contacts a so that the upper winding oi relay PA! is short circuited and the lower winding oi relay I'A'! is energized to reverse the flux in the relay and cause it to drop out quickly. The closing oi contacts a oi apparatus unit AU! also completes a shunt circuit around relay PT and an energizing circuit ior relay I'C' through contacts e oi relay 5'2. conductor relay I'C'. conductor Ii i. contacts e oi relay T'!, conductor III and contacts a of relay S'!. The closing oi contacts e oi relay I'C' completes an energizing circuit ior relay C'R. through conductor Bill, contacts a oi relay R'C'. contacts e oi relay I'C'. contacts a oi relay M'C'. contacts d oi relay 1"!" and contacts c oi relay R'C'. The opening oi contacts b oi relay C'R' interrupts the locking circuits oi relays Cl to 0'4, inclusive, P'l! and P' so that these relays drop out. The closing oi contacts d oi relay C'l reestablishes the energizing circuit oi relay O'D'. The opening oi contacts e oi relay P'i! and oi contacts e oi relay P'!l interrupts the heretoiore described energizing circuit ior relay MC'. which in turn by opening its contacts a interrupts the energizin circuit oi relay C'R'.

Thereiore. at the end oi the closing code. relays R'C', 8'2, C'H, TI. TI, O'D', I'C, IA'i. and TA! to I'A'l. inclusive. at the substation are energized. and the apparatus at the substation is now ready to transmit a close indication code to the dispatcher's oiilce. This close indication code is the same as the closing code; namely. iour positive impulses with a pause between the first and second impulses and between the second and third impulses.

The closing oi contacts I: oi relay C'R. at the termination oi the closing code completes an energizing circuit ior relay S'C' through contacts b oi relay C'R', conductor 400. contacts b oi relay 76 tacts b oi relay I'T', contacts c oi relay I'C'. con- C'l. contacts e oi. relay T'!, conductor Ill, concontacts d of relay C'B'.

tacts a of relay B'C', conductor 2. and contacts h oi relay U. The closing of contacts c of relay S'C' completes a locking circuit for this relay through contacts h of relay L'O', conductor 2, contacts 0 of relay S'C'. conductor 40! and contacts b of relay C'B'. The opening of contacts b of relay SC' interrupts the locking circuit of relay B'C', and the closing of contacts e of relay S'C' reestablishes the energizing circuit for relay US through contacts b of relay P'S', contacts b of relay L'X, conductorlll, contacts e of relay S'C', contacts I of relay C'l, conductor All and contacts d of relay C'B.

The apparatus at the substation then operates to eifect the transmission of the four impulses of the close indication code in the same manner that the four impulses of the selection check code were transmitted, except when C'l is energized by the first impulse the energizing circuit for relay P'S' is completed through contacts c of relay P'B, contacts h of relay C2, contacts h of relay C'2, contacts 1 of relay C'l, contacts e of relay CH', conductor 4, contact a of relay I'C, conductor I, contacts e of relay; B'C', contacts I of relay C'4, conductor 2 and contacts d of relay C'B'. Consequently, at the end of the first impulse, relay PR is deenergized and by closing its contacts b completes the heretofore described circuit for relay P I 2.

When C'2 is energized by the second impulse, the energizing circuit for relay P'S' is completed through contacts c of relay P'R, contacts In of relay 0'2, contacts 0 of relay C'2, contacts c of relay C'H', conductor 4, contacts e of relay SC', contacts I of relay C'l, conductor ill and Consequently, at the end of the second impulse, relay PR is deener- 'gized and by closing its contacts b completes the heretofore described circuit {or relay P'22.

At the completion of the fourth impulse, relay PR is again deenergized and closes its contacts d to complete an energizing circuit for relay M'C' through contacts h of relay P'2l, contacts e of relay P' l 2, contacts e of relay P'22, conductor Ill, contacts a of relay T'2, contacts i of relay 0', contacts a of relay S'C', contacts d of relay P'B', conductor 4, contacts e of relay T'l, conductor 2, contacts is of relay C'H', conductor "2, contacts I of relay L'O', conductor I02 and contacts h of relay B'L'. The closing of contacts a of relay M'C' completes an energizing circuit for the upper winding of relay I'A'2 through contacts c of relay 3'2, conductor 2, contacts I of relay BC', contacts e of relay I'C', contacts a of relay M'C', contacts d of relay IT', contacts d of relay B'C', conductor 3, contacts a of relay 8'2 and contacts a of apparatus unit AU2. The closing of contacts a of relay I'A'2 completes alocking circuit for the upper winding of this relay through contacts a of apparatus unit AU2.

The closing of contacts c of relay M'C' completes an energizing circuit for relay C'B' through contacts h of relay B'C and conductor llii. The opening of contacts I) of relay C'B' interrupts the holding circuits of relays C'l to 6'2, inclusive, P'l2, PM and S'C'. The closing of contacts d of relay 0'! reestablishes the energizing circuit for relay O'D', and the opening of contacts e of relay P'I2 and of contacts e of relay P'22 interrupts the energizin circuit of relay M'C', which in turn by opening its contacts c interrupts the energizing circuit of relay C'B'.

Therefore, at the termination or the close indication code, relays 8'2, C'H', T'l, T'2, O'D',

1'0, and I'A'l to I'A'l, inclusive, are energized at the substation.

The four impulses of the close indication code eifect the same operation of relays LB, 1.x, CI to 04, inclusive, CI, PB. OD, PM and P22 at the dispatchers omce as the closing code did, except that the energization of relay CT at the end of the first impulse of the indication code completes an energizing circuit for relay Bc through contacts e of relay CT, contacts b of relay 80, conductor 2| l and contacts I of relay BL.

At the termination of the fourth impulse of the indication code, time relays PB and OD successively become deenergized and drop out and a circuit is completed for the lower winding of relay MC through contacts h of relay'Pu, contacts e of relay Pl2, contacts e or relay P22, conductor 2, contacts 0 of relay BC, contacts a of relay T2, contacts i of relay Cl, contacts b of relay OD, contacts (1 of relay PB, contacts e of relay Tl, contacts 1 of relay CH, conductor 2 and contacts I of relay BL. The energization of relay MC completes an energizing circuit for relay 1B2 through resistor BB2, contacts a of relay 82, conductor I22, contacts a of relay MC, conductor 2 ll, contacts a of relay Cl and contacts a of relay BC. By closing its contacts c, relay 1B2 completes a locking circuit for itself through resistor BB2. The closing of contacts c of relay 1R2 completes a circuit for red lamp B2 through contacts b of key DK2, and the opening of contacts b oi relay 1R2 opens the circuits of the white lamp W2 and the green lamp G2. The lighting of the red lamp B2 informs the dispatcher that the apparatus unit AUI at the remote station is in its closed position.

The closing of contacts i of relay 1B2 completes an energizing circuit for relay CB through contacts 1 of relay 82, contacts i of relay 1B2, conductor Hi2, contacts i of relay MC, conductor 2",

contacts a of relay BC, conductor 2!, contacts 0 of relay P22, contacts e of relay 8T, contacts I:

of key MTK, contacts b of key CHK, contacts b of key MCK and conductor 222. The opening of contacts b of relay CB interrupts the locking circuits of relays CI to cl, inclusive, PH and P22. The closing of contacts I of relay Ci reestablishes the energizing circuit for relay OD, and the opening of contacts g of relay P22 interrupts the energizing circuit of relay CB. The opening of contacts e of relay P22 interrupts the heretofore described circuit for relay MC.

Therefore, at the termination of the close indication code, relays ST, 82, CH, T2, Tl, RC, OD, 155 BB and IE2 at the dispatchers ofiice are energized.

The dispatcher may now restore the equipment at the dispatchers omce and at the substation by restoring the select key 8K2 to its normal 60 position- The closing oi the contacts b of key 8K2 completes an energizing circuit for the lower winding of relay-L0 through contacts a of relay ST, conductor I00, contacts b of key SKI, contacts I) of key SKI, contacts b of key 8K2, con- 65 tacts b of key 8K2, contacts I) of key SKI, conductor 202, contacts d of relay Cl and contacts b of relay LX. The closing oi contacts c of relay L0 completes a locking circuit for the upper winding of relay LO through contacts h of relay 70 BL. The closing of contacts a of relay completes an energizing circuit for relay 18 through contacts I) of relay PS, contacts d of relay L'X,

conductor 222, contacts b of relay BL, conductor 2, contacts e of relay OD, conductor 22!, con- 76 tacts b of key ERK, conductor Ill, contacts a accuse 25 of relay DO, conductor '00, contacts (1 of relay Cl and contacts b of relay 1.1!. The encrgization of relay LB causes an impulse to ,be transmittedover line conductors Li and L2 so that relays LR and L)! are energized. The closing of contacts a of relay LX establishes the heretofore described energizing circuits for relays Cl and PR, and by closing its contacts a, relay Ci completes a locking circuit for itself and relay PR. in the manner heretofore described. The opening of contacts at of relay 1.x interrupts the energizing circuit of relay Ls so that it drops out and terminates the reset impulse being sent over line conductors LI and L2. The closing oi contacts b of relay LII completes the energization of relay CT in the manner heretofore described through contacts e of relay CI. The opening of contacts d of relay Ci prevents relay LS from being reenergized when relay 1.x closes its contact d. Consequently, relay PR. drops out aftera time delay and closes its contacts b to complete the heretofore described energizing circuit for relay Pli. The closing of contacts a oi relay Pi! completes a locking circuit for this relay through conductor "2 and contacts b of relay CR. The opening of contacts a of relay PR interrupts the energizing circuit for time relay OD, which after a time delay closes its contacts at and completes an energizing circuit for relay CR through conductor 810, contacts d of relay D, conductor 220, contacts e of relay LO, conductor 22! and contacts d of key EMK. Relay 0D also completes an energizing circuit for relay RL through the upper winding of release relay RL, conductor Ill, contacts I of relay OD, contacts 2) of relay C4, contacts a of relay Cl, conductor I02 and contacts b of relay CR. Due to the fact that relay CR. has a slightly slower operating characteristic, relay RL operates before relay CR opens its contacts b. The closing of contacts a of relay RL completes a locking circuit for this relay through the lower winding of relay RL, contacts a of relay RL, conductor 2 l s and contacts In of relay Ci so that relay BL remains energized after relay CR picks up. The opening of contacts 1 of relay RL interrupts the heretofore described locking circuits for relays 52, CH, Ti, T2 and BC. The opening of contacts h of relay BL interrupts the holding circuits of relays L0 and ST. The opening of contacts c of relay CH interrupts the heretofore described circuit for amber lamp A2.

The closing of contacts e of relay RL completes a shunt circuit around contacts e of relay LO, conductor 22! and contacts d of key EMK in the energizing circuit for relay CR through conductor 220, contacts d of relay OD and conductor 820. The closing of contacts a of relay CR completes a holding circuit for the lower winding of relay RL through contacts a of relay RL, conductor 2 l8 and contacts 0 of relay RL. The opening of contacts b of relay CR interrupts the circuit of upper winding of relay RL and the holding circuits of relays Cl, Pit and CT. The closing of contacts I of relay Cl reestablishes the heretofore described energizing circuit for relay CD, which by opening its contacts d interrupts the energizing circuit for relay CR. By opening its contacts a, relay CR. interrupts the holding circuit for the lower winding of relay RL so that it drops out.

The closing of contacts d' of relay Cl reestablishes the original circuit for start lamp STL which informs the dispatcher that the apparatus at the dispatchers oilice is in its normal-atrest position, ready for further operation.

At the substation, the single reset impulse effects the operation of relays L'R, UK, c i, C'T',

P'R' and P if in the same manner as the first impulse of the closing code. The closing of contacts e of relay C'T' completes an energizing circuit for s relay R'C' through conductor 4B2, contacts I) of relay S'C', conductor llli and conductor 500.

At the termination of the reset impulse, time delay relays FE and O'D' drop out in succession, and relay O'D' completes an energizing circuit for the upper winding of relay R'L through contacts b of relay O'D', contacts b of relay 0'4, contacts 0 of relay Cl, conductor 400 and contacts b of relay CR'. The closing of contacts a of relay RL' completes a holding circuit for the relay through its lower winding, conductor 402 and contacts e of relay C'l. The opening of contacts In of relay R'L' interrupts the holding circuit of relays Tl, Th8! and C'H'. The opening of contacts 0 of relay 8'! interrupts the energizing circuit of relay PC. The closing of contacts e of relay R'L' completes an energizing circuit for relay C'R' through contacts d of relay O'D' and conductor 805. The opening of contacts b of relay C'R" interrupts the energizing circuits of relays Cl. P' I! and C'T' and of the upper winding of relay R'L'. The closing of contacts at of relay C'l reestablishes the energizing circuit for relay O'D'. The opening of contacts at of relay O'D' interrupts the energizing circuit of relay C'R', and the opening of contacts a of relay C'R interrupts the energizing circuit of relays R'C' and R'L so that the substation equipment is back to its norto I'A'B, inclusive, energized.

If the dispatcher should want to open the apparatus unit AU! after closing it and before resetting the supervisory equipment, he may do so by momentarily operating the master tripping key MTK after the red lamp R2 is lighted. The op- 40 eration of the master tripping key MTK completes an energizing circuit for the upper winding of relay MT through contacts a of key MTK, conductor II I. contacts eof relay RC, contacts c of relay TI, contacts b of relay Ci. conductor 302 and contacts b of relay CR. The closing of contacts a of relay MT connects relay BC in parallel with the upper winding of relay MT through conductor "I so that relay SC closes its contacts e and completes a locking circuit for itself and the upper winding of relay MT through conductors Jill and it! and contacts b of relay CE. The opening of contacts b of relay SC interrupts the locking circuit of relay RC. and the closing of contacts c of relay SC completes the heretofore described energizing circuit for relay L5 to effect the transmission of the tripping code of four impulses over line conductors LI and L2. This tripping code includes two pauses, one between the second and third impulses and the other between the third and fourth impulses, which pauses are effected in the manner heretofore described by the energization of relay PB.

At the dispatcher's office, the fourimpulses of the tripping code effect the operation of relays 65 1.1:, CI to Cl, inclusive, CT, OD and PR in the same manner as the four impulses of the closing code. when relay CI is energized in response to the second impulse, its contacts a complete an energizing circuit for relay PB through conductor 70 800, contacts b of relay LO, conductor 2, contacts c of relay PR, conductor I01, contacts I of relay CI, contacts a of relay C2. conductor ill,

contacts a of relay CH, conductor tit, contacts a of relay OD, contacts b of relay Cl, contacts a 76 of relay Cl, conductor I02 and contacts b of relay mal-at-rest position with relays O'D' and I'A'i amazes CR. When relay C2 is energised by the third impulse of the tripping code. its contacts 1 complete an energizing circuit for relay P8 through conductor 3, contacts I: of relay LO, conductor 2, contacts c of relay PR, conductor 3", contacts i of relay C3, conductor 2", contacts e of relay CH, conductor 2", contacts I of relay Pl2, conductor Sil contacts a of relay D, contacts b of relay C4, contacts a of relay Cl, conductor 2 and contacts I) of relay CR.

When relay PR drops out and closes its contacts d in response to the pause between the second and third impulses, relay P22 is energized and completes a locking circuit for itself in the manner heretofore described. Similarly, when relay PR drops out in response to the pause between the third and fourth impulses of the trippinieode, relay PM is energized and completes a locking circuit for itself. -At the termination of the tripping code, time relay PR drops out and completes the heretofore described energizing circuit for relay CR, which by opening its contacts b interrupts the locking circuits of relay CI to Cl, inclusive, P22, P24 and BC and the circuit of the upper windingof relay MT. The opening of contacts t of relay CI interrupts the energizing circuit for relay CR, and

the closing of contacts I of relay Cl reestabllshes the heretofore described energizing circuit for relay 0D. 1

At the substation, the four impulses of the tripping code effect the operation of relays L'R', LX', Ql to 0'4, inclusive, C'T', O'D' and FR in the same manner as the four impulses of the closing code. The pause between the second and third impulses is of sufllcient duration to allow relay P'R' to drop out and close its contacts b thereby completing the heretoforedescribed circuit for code register relay P22. Similarly, the

pause between the third and fourth impulses of the tripping code is of sufllcient durationto allow relay P'R' to drop out and complete the heretofore described energizing circuit for code register relay P'Sl.

At the termination of the fourth and last impulse of the tripping code, relay PR is again deenergized and by opening its contacts 0 effects after a time delay the deenergization of relay O'D. The closing of contacts I of relay O'D' completes an energizing circuit for master tripping relay MT' through contacts i of relay P'll, contacts d of relay P'l2, contacts e of relay P'22, conductor SIB, contacts a of relay T'2, contacts i of relay 0', contacts I of relay O'D. contacts d ofrelay P'R, conductor 4, contacts e of relay T'l, conductor 2, contacts In of relay C'H', conductor 402, contacts I of relay LO, conductor 503 and contacts h of relay R'L. The closing of contacts 0 of relay M'T' completes an energizing circuit for the trip coll T0 of apparatus unit AU2 throughcontacts e of relay R'C', conductor 5|, contacts a of relay 0', conductor 1, contacts b of relay M'C', contacts e of relay M'T', conductor 52: and contacts i of relay S'2.

The, opening of apparatus unit AU: opens its contacts a and closes its contacts b so that the upper winding of relay I'A'2 is short circuited and the lower winding of relay I'A'2 is energized to reverse the flux in the relay and cause it to drop out quickly. The closing of contacts b of apparatus unit AU2 also completes a shunt circuit around relay 1'0 and an energizing circuit for relay I'T through contacts b of apparatus unit AU2, contacts a of relay 8'2, conductor 2. contacts e of relay T2 and conductor II I. The

28 closing'of contacts e of relay 1"!" completes an energizing circuit for relay C'R' through conductor I", contacts 9 of relayR'C', contacts d of relay I'C', contacts a of relay MT', contacts 5 e of relay 1"!" and contacts c of relay 3/0. The opening of contacts I) of relay C'R"restores the apparatus at the substation to the same condition it was in at the end of the closing code, except-that relay I'T' instead of relay I'C' is energized. The apparatus at the substation is now ready to transmit a trip indication code to the dispatcher's omce.

The closing of contacts b of relay C'R' at the termination of the tripping code completes an energizing. circuit for relay S'C' through contacts b of'relay CR', conductor 4", contacts b of relay C'l, contacts c of relay T'2, conductor Ill. contacts 0 of relay I'T', contacts b of relay I'C', contacts a of relay RC', conductor 2 and contacts h of relay U0. The opening of contacts b of relay S'C' deenergizes relay RC'. The closing of contacts 0 of relay SC' reestablishes the energizing circuit for relay L'S' in the manner heretofore described so that the four impulses of thetrip indication code are transmitted over line conductors LI and L2. This trip indication code, which is the same as the tripping code, includes two pauses, one between the second and'third impulses and the other between the third and fourth impulses, which are eflected in the manner heretofore described by the energization of relay P'B'. At the substation, the four impulses of the trip indication code effect the operation of relays L'X', C'I to 0'4, inclusive, C'T', O'D' and P'R' in the same manner as the four impulses of the tripping code. When relay C'2 is energized in response to the second impulse, its contacts g complete an energizing circuit for relay P'S' through contacts 0 of relay P'R', contacts h of relay 0'2, contacts a of relay 0'2, contacts c of relay C'H, conductor 40. and contacts e of relay S'C', contacts I of relay 0'4, conductor Ill and contacts d of relay C'R'. When relay C is energized in response to the third impulse, anenergizing circuit is completed for relay P'S' through contacts c of relay P'R', contacts i of relay 0'2, contacts a of relay CH', conductor 422, contacm I of relay P'l2, conductor 4", con- 5 tacts e of relay SC', contacts I of relay C'l.

conductor ill and contacts at of relay C'R. When relay P'R' drops out in response to the pause between the second and third impulses, relay P22 is energized and completes a locking 55 circuit for itself inthe manner heretofore described. Similarly, when relay P'R. drops out in response to the pause between the third and fourth impulses, relay P' is energized and conipletes a locking circuit for itself.

At the termination of the trip indication code,

time relay P'R' drops out and completes an energizing circuit for relay M'T' through contact i of relay P'fl, contacts a of relay P'l2, contacts e of relay P'22, conductor III, contacts a of relay T'2, contacts 1 of relay 0'4, contacts a of relay SC', contacts at of relay P'R'. conductor 4, contacts e of relay Tl, conductor 2. contacts k of relay CH', conductor 2, contacts I of relay L'O', conductor ill, and contacts In of relay R'L. The closing of contacts a of relay M'T' energizes lower winding of relay I'A'2 through contacts c of relay 8'2, conductor til, contacts I of relay R'C', contacts :1 of relay I'C', contacts a of relay M'T, contacts e of relay 1'1",

76 contacts 1.! of relay RC'. conductor lit, contacts 

